The role of the left ventrolateral prefrontal cortex in online sentence processing
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1
Johns Hopkins University, Neurology Department, United States
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2
Drexel University, Psychology Department, United States
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3
Moss Rehabilitation Research Institute, United States
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4
University of Pennsylvania, Psychology Department, United States
Introduction: Patients with damage to the left ventrolateral prefrontal cortex (VLPFC) are often not impaired in understanding simple sentences. It is, however, possible that the damage may cause subclinical effects. If VLPFC has a role in biasing competition towards what is relevant to the task, we would expect patients with VLPFC damage to be slower in using the relevant information and discarding the irrelevant information when they process sentences online.
Methods: Nine patients, five with lesions limited to VLPFC, and four with lesions sparing VLPFC participated. The groups were matched in age, education, WAB-AQ and total lesion volume. Two experiments explored processing of online cues during sentence comprehension by tracking eye fixations in a Visual World paradigm with four pictures. Participants only listened to the sentences and looked at the pictures.
Experiment 1 investigated how quickly cues can be used for target identification using a simple “She will [verb] the [target].” sentence structure. The verbs in the restrictive condition were compatible with only one of the four pictures (e.g., “eat”; target “apple” + three inedible competitors). The verbs in the control conditions were matched to the restrictive verbs in length and frequency, but did not point to a unique target (e.g., “see”). If VLPFC is critical for quickly biasing competition towards the relevant target, the VLPFC patients should to be slower than the non-VLPFC patients in fixating the noun when the verb is restrictive.
Experiment 2 probed how effectively irrelevant cues are suppressed. A similar Visual World paradigm was used, but all verbs were restrictive, and one of the distractors was also compatible with the verb (e.g., “banana”). The sentences contained an adjective that ruled out one of verb-compatible pictures (e.g., “red”). The critical manipulation involved a third picture (the adjective competitor) which was compatible with the adjective, but not with the verb (e.g., “heart”; note that all pictures were black and white line drawings). The control condition was similar, except that the adjective competitor was replaced by a picture compatible with neither the verb, nor the adjective (e.g., “frog”). If VLPFC is important for biasing competition away from the irrelevant information, we expect the VLPFC lesion group to exhibit more continued looks to the adjective competitor compared to the non-VLPFC lesion group.
Results: Data are shown in Fig. 1.The data were analyzed using Growth Curve Analysis. Experiment 1: In the time window from the verb onset to noun onset, the VLPFC lesion group exhibited reliably less target anticipation than the non-VLPFC lesion group (patient group* condition interaction: t = 10.632, p < 0.001). Exp. 2: In the time window from the adjective onset to the end of the sentence, the VLPFC lesion patients were significantly more likely to fixate the adjective competitor (e.g., “heart”) than the non-VLPFC patients were (patient group* condition interaction: t = 2.615; p = .009).
Conclusions: The results are compatible with a biasing competition role of VLPFC in sentence production: VLPFC facilitates processing of the relevant information and inhibits processing of the irrelevant information.
Acknowledgements
We would like to thank the patients and the staff at Moss Rehabilitation Research Institute for their contribution to this research.
Keywords:
Aphasia,
vlPFC,
LIFG,
Eye-tracking,
sentence comprehension,
Prefrontal Cortex,
inferior frontal gyrus,
language acquisition
Conference:
Academy of Aphasia -- 52nd Annual Meeting, Miami, FL, United States, 5 Oct - 7 Oct, 2014.
Presentation Type:
Platform or poster presentation
Topic:
Not student
Citation:
Nozari
N,
Mirman
D and
Thompson-Schill
SL
(2014). The role of the left ventrolateral prefrontal cortex in online sentence processing.
Front. Psychol.
Conference Abstract:
Academy of Aphasia -- 52nd Annual Meeting.
doi: 10.3389/conf.fpsyg.2014.64.00012
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Received:
21 Apr 2014;
Published Online:
04 Aug 2014.
*
Correspondence:
Dr. Nazbanou Nozari, Johns Hopkins University, Neurology Department, Baltimore, United States, bnozari@andrew.cmu.edu